Due to the increasingly strict requirements imposed in terms of environmental friendliness, hydrocarbon (HC) emissions are taken increasingly into account in vehicles operated with fuel, e.g., gasoline. The emission of waste gases, especially HC waste gases, is determined in so-called SHED (Sealed Housing for Evaporative Determination) tests and compared with corresponding limit values.
Since fuel-operated heating systems are increasingly used, for example, as parking heaters or auxiliary heaters in motor vehicles, the fact that such heating systems can also contribute to the waste gases generated in a vehicle shall be taken into account concerning the waste gas emissions. Such a vehicle heating system is, in principle, open towards the outside, i.e., towards the environment in both the area of the waste gas removal system and the area of the combustion air feed system. Unburned fuel still present, for example, in a combustion chamber after the end of the operation can lead to HC waste gas and its emission into the environment.